川西须家河组二段岩石可钻性实验分析

Experimental Analysis on Rock Drillability of Xu2 Formation in Western Sichuan

川西坳陷须家河组存在可钻性差、机械钻速低等严重制约钻井效率的问题。以川西坳陷须家河组二段地层所采岩样为研究对象,利用自主研发的HTHP岩石可钻性试验仪对模拟井底围压及液柱压力条件下的岩样进行可钻性级值测试,并从岩样的岩石力学性质及微观组构等方面开展研究,以此分析其对岩石可钻性的影响。结果表明:围压及液柱压力的增加导致岩石可钻性级值及抗压强度的增加,抗压强度与可钻性级值成正比。高抗压强度条件下的可钻性级值增长率降低;岩石的研磨性及硬度会影响岩石的可钻性。岩石中石英含量越高、黏土矿物含量越少,岩石研磨性及硬度越高,岩石可钻性级值越大。

The Xujiahe Formation in the West Sichuan Sag has the problems of poor drillability and low penetration rate which could severely restrict drilling efficiency.However,there are no systematic studies on the factors affecting the drillability of this horizon.The rock samples from the second member of Xujiahe Formation in the West Sichuan Sag are taken as the research object.The self-developed HTHP rock drillability tester was used to obtain the drillability grade values under the conditions of simulated bottom hole confining pressure and liquid column pressure.The rock mechanics properties and microstructure of the rock samples are studied in order to analyze their influence on the rock drillability.The results show that the increase of confining pressure and liquid column pressure leads to the increase of rock drillability and compressive strength,and the compressive strength is proportional to the drillability grade value.The growth rate of the drillability grade under high compressive strength is reduced;the abrasiveness and hardness of the rock can affect the drillability of the rock.Higher quartz content in the rock and less clay mineral content will cause higher abrasiveness and hardness of the rock,and lead to greater rock drillability value.